Inverse multiplexer device

ABSTRACT

The inverse multiplexer device for inverse multiplexing of a broadband data stream received via a broadband data line ( 7 ) comprising measuring means ( 3   a - 6   a ) for measuring connection parameters of data transmission lines ( 3 - 6 ) connected in parallel to each other, selection means for selecting a subset of the data transmission lines ( 3 - 6 ) depending from the measured connection parameters and activation means ( 15   a ) for activating he selected subset of data transmission lines ( 3 - 6 ) to transmit the received data transmission stream over the selected subset of data transmission lines ( 3 - 6 ).

[0001] The invention relates to an inverse multiplexer device forinverse multiplexing of a broadband data stream received on a broadbanddata line via a plurality of data transmission lines such astwisted-pair telephone copper lines.

[0002] Inverse multiplexing techniques can be used to support higherfrequency bandwidth data transmission using several connections insteadof a single broadband connection such as a fibre-optic cable or coaxiallink. IMA-is an inverse multiplexing technique related to. ATM E1/T1connections. The inverse multiplexing protocol for ATM used by IMA doesnot relate to the data transfer medium. In the IMA-inverse multiplexingtechnique the data transfer quality of connection lines is not measuredand evaluated.

[0003] As can be seen from FIG. 1 a plurality of DSL-connection lines isprovided within a cable trunk. Each DSL-connection line consists of atwisted-pair telephone line made of copper. Environmental noise andsignal disturbances created by other DSL-connection lines within thesame cable trunk and the signal attenuation of the twisted-pairtelephone line limit the amount of total bandwidth available over theaggregated connection lines. The cross-talk between the differentDSL-connection lines reduces the possible operating distance for datatransmission. Since in the IMA inverse multiplexing technique thequality of the data transmission line is not evaluated a datatransmission line is activated which does not provide the best possibledata transmission.

[0004] Accordingly it is an object of the present invention to providean inverse multiplexer device and a method for inverse multiplexingwhich provides a high reliability of the data transmission throughmultiple data transmission lines.

[0005] The present invention provides an inverse multiplexer device forinverse multiplexing of broadband data stream received via a broadbanddata line comprising:

[0006] measuring means for measuring connection parameters of datatransmission lines connected in parallel to each other,

[0007] selection means for selecting a subset of the data transmissionline depending from the measured connection parameters, and

[0008] activation means for activating the selected subset of datatransmission lines to transmit the received broadband data stream overthe selected subset of data transmission lines.

[0009] In a preferred embodiment of the inverse multiplexer deviceaccording to the present invention the data transmission lines areDSL-connection lines.

[0010] The DSL-connection lines consists preferably of twisted-paircopper lines.

[0011] In a preferred embodiment the measuring means measuresintra-connection parameters, cross-connection parameters andgeneral-connection parameters of the data transmission line.

[0012] The intra-connection parameters measured by the measuring meansare preferably the bit error rate BER, the signal to noise ratio SNR andthe spectral line characteristic of each transmission line.

[0013] The cross-connection parameters measured by the measuring meansare preferably the cross-talk magnitudes of cross-talk between all datatransmission lines. The general-connection parameters measured by themeasuring means are preferably ambient noise magnitudes of ambient noiseeffecting the data transmission lines. In a preferred embodiment theinverse multiplexing device according to the present invention comprisesseveral DSL-modems wherein each modem is connected to one datatransmission line.

[0014] Each modem measures preferably the connection parameters of therespective data transmission line.

[0015] In a further preferred embodiment of the inverse multiplexerdevice according to the present invention the data transmission linesconnect the inverse multiplexer device to a demultiplexing device fordemultiplexing the data stream transmitted by the inverse multiplexingdevice via the data transmission lines.

[0016] The broadband data line for transmitting the broadband datastream to the inverse multiplexer device is preferably a glass fibre,100 base T or a coax cable.

[0017] The inverse multiplexing device according to the presentinvention is in a preferred embodiment connected via the data line to achopper device for chopping the received broadband data stream into datacells of a predetermined size.

[0018] The demultiplexing device comprises in a preferred embodimentdata reception buffers wherein each reception buffer is connected to arespective data transmission line for buffering data cells multiplexedby the inverse multiplexer device.

[0019] The demultiplexing device is connected in a preferred embodimentto a reconstructor for reordering the data cells using tags attached toeach data cell generated by the chopper device.

[0020] The broadband data stream received by the inverse multiplexerdevice according to the present invention is preferably a PDH-datastream, SDH-data stream, a ATM-data stream, an Ethernet-data stream, aHDLC-data stream or a SONET-data stream.

[0021] In a further preferred embodiment of the inverse multiplexerdevice according to the present invention the selection means is acentral processing unit CPU.

[0022] The central processing unit CPU is in a preferred embodimentintegrated within the inverse multiplexer device according to thepresent invention.

[0023] The present invention further provide a multiplexer system formultiplexing a broadband data stream to transmit the broadband datastream via a plurality of data transmission lines connected in parallelto each other comprising the inverse multiplexing device and ademultiplexing device connected to the inverse multiplexing devicethrough he plurality of data communication lines.

[0024] The present invention provides further a method for inversemultiplexing of broad band data streams, wherein

[0025] the connection parameters of a plurality of data transmissionlines are measured,

[0026] a subset of the plurality of data transmission lines is selecteddepending from the measured connection parameters,

[0027] and wherein the selected subset of data transmission lines isactivated to transmit the broadband data stream via the selected subsetof data transmission lines.

[0028] The data transmission lines are measured preferably subsequently.

[0029] In a preferred embodiment of the method for inverse multiplexingaccording to the present invention for each data transmission lineintra-connection parameters, cross-connection parameters and generalconnection parameters are measured separately.

[0030] In a further preferred embodiment of the method for inversemultiplexing according to the present invention the measured connectionparameters of all data transmission lines are used to generate aconnection parameter matrix.

[0031] The data transmission lines which are not selected are preferablydeactivated.

[0032] The measuring of the data transmission lines is in a preferredembodiment of the method according to the present invention repeatedperiodically. In a still further embodiment of the method for inversemultiplexing according to the present invention a deactivated datatransmission line is selected and activated to substitute an activateddata transmission line when the connection parameters of the activateddata transmission line indicate that the data transmission through thisdata transmission line has degraded.

[0033] Preferred embodiments of the inverse multiplexer device and themethod for inverse multiplexing according to the present invention aredescribed in detail with respect to the attached figures.

[0034]FIG. 1 shows a cross section through a cable trunk consisting of aplurality of data transmission lines to explain the problem underlyingthe present invention.

[0035]FIG. 2 shows one data path of a multiplexer system formultiplexing a broadband data stream via a plurality of datatransmission lines connected in parallel to each other including aninverse multiplexer device IMUX according to the present invention.

[0036]FIG. 3 shows a block diagram of an inverse multiplexer device IMUXaccording to the present invention.

[0037]FIG. 4 is flow chart of a preferred embodiment of the method forinverse multiplexing of a broadband data stream according to the presentinvention.

[0038] In FIG. 2 one data path of a multiplexer system for multiplexinga broadband data stream includes an inverse multiplexing device 1according to the present invention. The multiplexer system comprises twoseparated data paths for bidirectional data transmission. The inversemultiplexing device 1 is connected to a demultiplexing device 2 througha plurality of data transmission lines 3, 4, 5, 6 such as twisted-pairtelephone wires made of copper. The inverse multiplexer device 1includes several data transfer modems 3 a, 4 a, 5 a, 6 a to transmitdata cells through data transmission lines 3, 4, 5, 6 to data modems 3b, 4 b, 5 b,-6 b within the demultiplexing device 2. The inversemultiplexing device 1 according to the present invention is connected toa broadband data line 7 and receives a broadband data stream over thebroadband data line 7 from a chopper device 8. The chopper device 8receives a broadband data stream from a data source through a data line9 and chops the broadband data stream received via a data line into datacells having a predetermined fixes size. The original data stream online 9 is transmitted as payload inside the data cells D generated bythe chopper device 8.

[0039] The inverse multiplexer device 1 according to the presentinvention receives the data cell D and performs an inverse multiplexingto distribute the received data cells for data transmission over asubset of data transmission lines which provide the highest reliabilityfor data transmission.

[0040] The demultiplexing device 2 demultiplexes the data streamstransmitted by the inverse multiplexer device 1 via the selected subsetof transmission lines and sends the demultiplexed data cells through adata line 10 to a reconstructor 11 for reordering the data cells D.

[0041] The inverse multiplexing device 1 transmits the data cells Dreceived from the chopper 8 through the selected active datatransmission lines in known order. The demultiplexer 2 receives the datacells in a different order due to connection delay differences.Accordingly the order of the data cell D sent by demultiplexer 2 vialine 10 differs from the order of data cells D received by the inversemultiplexing device via line 7. The reconstructor 11 reorders the datacell using tags attached to each data cell by the chopper device 8during the generation of the data cell D. The reconstructor 11 reordersthe data cell to get the original data stream received by the chopperdevice 8 via line 9. The data cells which has been reordered by thereconstructor 11 are output through the data line 12 for further dataprocessing.

[0042] The inverse multiplexing device 1 and the demultiplexing device 2are both connected through lines 14, 16 to a central processing units 15a, 15 b for data management and multiplexing control.

[0043]FIG. 3 shows a block diagram of an inverse multiplexer device 1according to the present invention. The inverse multiplexing device 1includes several modems 3 a, 4 a, 5 a, 6 a each connected to arespective data transmission line 3 to 6. Each modem 3 a-6 a isconnected through lines 13 a-16 a to a data transmission terminal 17 ofthe inverse multiplexing device 1. Further each modem 3 a-6 a isconnected via lines 13 b-16 b to data transmission terminals 13 c-16 cfor connecting the inverse multiplexing device 1 with the datatransmission lines 3-6. Each modem 3 a-6 a measures the connectionparameters of the respective data transmission lines 3-6 and transfersthe measured connection parameters via respective parameter transferlines 13 d-16 d to a parameter transfer terminal 18 of the inversemultiplexing device 1. The parameter transfer terminal 18 is connectedto the central processing unit 15 a which receives the measuredconnection parameters of all data transmission lines 3-6 and stores theconnection parameters into storage means 19 connected to the centralprocessing unit 15 a via a line 20 for further evaluation of theconnection parameters.

[0044] In a preferred embodiment of inverse multiplexing device 1 thecentral processing unit 15 a and the storage means 19 for storing themeasured connection parameters are integrated in the inversemultiplexing device 1.

[0045] Modems 3 a-to 6 a are preferably DSL-modems. Each DSL-modem 3 a-6a measures intra-connection parameters, cross-connection parameters andgeneral-connection parameters of the respective connection line 3-6.

[0046] The intra-connection parameters measured by the modem are the biterror rate BER, the signal-noise-ratio SNR and the spectral linecharacteristic of the data transmission line 3-6. The cross-connectionparameters measured by a modem 3 a-6 a are the cross-talk magnitudes ofcross talk between the respective connection line and the otherremaining connection lines.

[0047] As general-connection parameters the modems 3 a-6 a measure theambient noise magnitudes of ambient noise effecting the respectiveconnection line.

[0048] The measured connection parameters of all connection lines 3-6are stored by the central processing unit 15 in storage means 19. On thebasis of the stored connection lines parameters a parameter matrix P isgenerated by the central processing unit 15 a before the selection of anoptimal subset of data transmission lines 3-6. ${P = \begin{bmatrix}A_{1,1} & A_{1,2} & \quad & \quad \\A_{2,1} & A_{2,2} & \quad & \quad \\\quad & \quad & ⋰ & \quad \\\quad & \quad & \quad & A_{N,{N - 1}} \\\quad & \quad & A_{{N - 1},N} & A_{N,N}\end{bmatrix}}$

[0049] Wherein A_(ii) are the intra channel quality parameters based onbit error rate BER, signal to noise ratio SNR, wherein A_(ij) are crosschannel quality parameters based on cross talk between different datatransmission lines, and wherein N is the number of all available datatransmission lines connecting the inverse multiplexing device 1 to thedemultiplexing device 2 as shown in FIG. 2.

[0050] In the example shown in FIG. 2 the number N of available dataconnection lines is four. The central processing unit evaluates theparameter matrix P and selects a subset of K data transmission linesfrom a total of N available connection lines, wherein the subset of Kdata connection lines selected by the central processing unit providesfor the highest reliability in data transmission between the inversemultiplexing device 1 and the demultiplexing device 2.

[0051] After selection of the best subset of data transmission lines thecentral processing unit 15 a activates the respective modems 3 a-6 a viacontrol lines 13 e-16 e connected to a control terminal 21 for datatransmission. The modems of the remaining not selected data transmissionline are deactivated. During the selection process the centralprocessing unit 15 a scores all DSL-connections from the best datatransmission connection to the worst data transmission connection line.The best K data transmission line needed to transport the requiredbandwidth are turned on. The rest of the data transmission lines areturned off. The process of data line quality measurement takes place inall active data transmission lines K. In case of a data line failure dueto disconnection or in case of a very high bit error rate of anactivated data transmission line this data transmission line is turnedoff by deactivating the respective modem and the best next availabledata transmission line is turned on to substitute the defect datatransmission line.

[0052] The measurement of the connection parameters of the datatransmission line is repeated periodically. Switching occurs when one ofthe data transmission lines is disconnected or has a high bit error rateBER. Using a set of N data connection lines with a theoretical bandwidthwhich is wider than the requested bandwidth for data transmission andselecting the best subset of data connection line provides a high faulttolerance and better connection quality in terms of bit error rate BERor signal to noise ratio SNR. The selection of the best subset of dataconnection lines is performed automatically and the dynamicallyswitching between all available data connection lines provides bestaggregated data transmission connection between the inverse multiplexingdevice 1 and the demultiplexing device 2.

[0053] In the example shown in FIG. 2 the central processing unit 15 aselects as an optimal subset of data transmission line the datatransmission line 3, 4, 5 whereas the data transmission line 6 isswitched off. In case that, e.g. data transmission line 3 isdisconnected data transmission line 6 will be switched on by the centralprocessing unit 15 to substitute the disconnected data transmission line3. The data transmission lines which are not switched on by the centralprocessing unit 15 a provide for a redundancy in the data transmission.In case that a higher frequency bandwidth is necessary for datatransmission back-up data transmission lines can be switched on toprovide for the necessary total frequency bandwidth.

[0054] The data connection can be based on any DSL-technology such asHDSL, SDSL, ADSL or VDSL. The broadband data stream received by theinverse multiplexing device 1 through broadband data line 7 can be anykind of data stream such as PDH-data stream, SDH-data stream, ATM-datastream, Ethernet-data stream, HDLC-data stream or a SONET-data stream.The multiplexing system shown in FIG. 2 can be used both in the upstreamand in the downstream data transfer direction when using DSL-technology.The central processing units 15 a, 15 b on both sides handle theselection process and the redundant line switching process. The inversemultiplexing device 1 guarantees a high bandwidth, full duplex data bitstream from point to point via the best K data connection lines with anaggregated bandwidth. The other N-K data connection lines are used asback-up links for the system. The detection of a fault data connectionline in terms of bit error ratio BER or signal to noise ratio SNR willlead to hot swapping of the faulty data connection line with the bestavailable back-up link.

[0055] The inverse multiplexing device 1 according to the presentinvention can be powered locally from a powers source or can be poweredremotely over the connections lines.

[0056] The twister-pair data connection lines can connect a centraloffice exchange to a cabinet or curb, a curb to a basement or an enduser or two rooms inside the same building. The inverse multiplexingdevice 1 reduces the costs for high-speed data transmission to a wideextend because conventional data transmission lines can be used for abroadband data transmission. The transferred data are transmitted overthe same connection medium such as cable trunk thus introducing a verysmall time delay. The multiplexer system shown in FIG. 2 supplies highbandwidth connection without the need of installing an expensive newfibre optic connection. Existing copper based twisted pairs are usedinstead.

[0057]FIG. 4 shows a preferred embodiment for a method for inversemultiplexing of a broad band data stream according to the presentinvention.

[0058] The process starts with step 0 and in step 1 all transmittersT_(x), i.e. modems 3 a-6 a within the inverse multiplexing device areturned off.

[0059] In step S2 the ambient noise on all receivers Rx, i.e. modems 3b-6 b within the demultiplexing device 2 is measured.

[0060] In step S3 the first transmitter, i.e. modem 3 a within inversemultiplexing device 1 is turned on.

[0061] In step S4 it is checked whether the receiver 1, i.e. modem 3 bwithin the demultiplexing device 2, is locked to the transmitting device3 a.

[0062] In case that modem 3 b within the demultiplexing device 2 islocked to respective transmitting device 3 a the bit error ratio BER andthe spectral line characteristic of the data transmission line 3 ismeasured as intra-connection parameters of the data transmission linewithin step S5.

[0063] In a further measuring step S6 the cross-talk between the datacommunication line 3 and the remaining other communication lines 4-6 ismeasured.

[0064] The process continues with step S7 wherein all operatingtransmitting devices are turned off again.

[0065] Then in step S8 the next transmitting device such as modem 4 awithin the inverse multiplexing device 1 is turned on and the measuringsteps S4 to S6 are repeated. This in done for all transmitting devices 3a-6 a of the inverse multiplexing device 1 until in step 10 it isdetected that the connection parameters of the last data transmissionline have been measured.

[0066] After all connection parameters have been detected a parametermatrix P is generated in step S11.

[0067] The central processing unit 15 a selects the best K dataconnection lines on the basis of the parameter matrix P in step S12.

[0068] In step S13 the modems of the selected data transmission linesare activated by the central processing-unit 15 for data transmission.

[0069] The process shown in FIG. 4 it stops in step S15.

[0070] The measuring of the data transmission lines is repeatedperiodically. A deactivated data transmission line is selected andactivated to substitute an activated data transmission line when theconnection parameters of the activated data transmission line indicatethat the data transmission through this data transmission line hasdegraded.

1. An inverse multiplexer device for inverse multiplexing of a broadbanddata stream received via a broadband data line (7) comprising: measuringmeans (3 a-6 a) for measuring connection parameters of data transmissionlines (3-6) connected in parallel to each other; selection means forselecting a subset of the data transmission lines (3-6) depending fromthe measured connection parameters; and activation means (15 a) foractivating he selected subset of data transmission lines to transmit thereceived data transmission stream over the selected subset of datatransmission lines.
 2. The inverse multiplexer device according to claim1, wherein the data transmission lines (3-6) are DSL-connection lines.3. The inverse multiplexer device according to claim 2, wherein theDSL-connection lines (3-6) are twisted-pair telephone copper lines. 4.The inverse multiplexer device according to one of he preceding claims,wherein the measuring means (3 a-6 a) measure intra-connectionparameters, cross-connection parameters and general-connectionparameters.
 5. The inverse multiplexing device according to one of thepreceding claims, wherein the intra-connection parameters measured bythe measuring means (3 a-6 a) are bit error rates (BER), signal to noiseratio (SNR) and spectral line characteristic of each data transmissionlines (3-6).
 6. The inverse multiplexer device according to one of thepreceding claims, wherein the cross-connection parameters measured bythe measuring means (3 a-6 a) are cross talk magnitudes of cross talkbetween a respective data transmission line and the remaining other datatransmission lines.
 7. The inverse multiplexing device according to oneof the preceding claims, wherein the general connection parameters areambient noise magnitudes of ambient noise effecting the datatransmission via the data transmission line (3-6).
 8. The inversemultiplexing device according to one of the preceding claims, whereinthe inverse multiplexing device (1) comprises several DSL-modems (3 a-6a), wherein each modem is connected to one respective data transmissionline (3-6).
 9. The inverse multiplexing device according to one of thepreceding claims, wherein DSL-modem (3 a-6 a) measures the connectionparameters of the respective data transmission line (3-6).
 10. Theinverse multiplexing device according to one of the preceding claims,wherein the data transmission lines (3-6) connect the inversemultiplexing device (1) with a demultiplexing device (2) fordemultiplexing the data streams transmitted by the inverse multiplexingdevice (I) via the data transmission lines (3-6).
 11. The inversemultiplexing device according to one of the preceding claims, whereinthe broadband data line (7) is a glass fibre, 100 base T or coax cable.12. The inverse multiplexing device according to one of the precedingclaims, wherein the inverse multiplexing device (1) is connected via thebroadband data line (7) to a chopper device (8) for chopping thereceived broadband data stream into data cells D of a predeterminedsize.
 13. The inverse multiplexing device according to one of thepreceding claims, wherein the demultiplexing device (2) comprisesreception data buffers, wherein each buffer is connected to a respectivedata transmission line (3-6) for buffering data cells D multiplexed bythe inverse multiplexing device (1).
 14. The inverse multiplexing deviceaccording to one of the preceding claims, wherein the demultiplexingdevice (2) is connected to a reconstructor (11) for reordering the datacells D using tags attached to each data cell generated by the chopperdevice (8).
 15. The inverse multiplexing device according to one of thepreceding claims, wherein the broadband data stream is a PDH-datastream, a SDH-data stream, an ATM-data stream, an ETHERNET-data stream,a HDLC-data stream or a SONET-data stream.
 16. The inverse multiplexingdevice according to one of the preceding claims, wherein the selectionmeans and the activation means are formed by a central processing unit(15 a) integrated within the inverse multiplexing device (1). 17.Multiplexing system for multiplexing a broadband data stream to transmitthe data stream via a plurality of data transmission lines (3-6)connected in parallel to each other comprising the inverse multiplexingdevice (1) according to claim 1 and a demultiplexing device (2)connected to the inverse multiplexing device (1) through the pluralityof data transmission lines (3-6).
 18. The method for inversemultiplexing of a broadband data stream comprising the following steps:(a) measuring the connection parameters of a plurality of datatransmission lines (₃₋₆); (b) selecting a subset of the plurality ofdata transmission lines (2-6) depending from the measured connectionparameters; (c) activating the selected subset of data transmissionlines (2-6) to transmit the broadband data stream via the selectedsubset of data transmission lines (3-6).
 19. The method according toclaim 18 wherein all data transmission lines (3-6) are measuredsubsequently.
 20. The method according to one of the preceding claims 18to 19, wherein for each data transmission line (3-6) intra-connectionparameters, cross-connection parameters and general connectionparameters are measured.
 21. The method according to one of thepreceding claims 18 to 20, wherein a connection parameter matrix P isgenerated depending from the measured connection parameters of all datatransmission lines (3-6).
 22. The method for inverse multiplexingaccording to one of the preceding claims 18 to 21, wherein the datatransmission lines (2-6) which have not been selected are deactivated.23. The method for inverse multiplexing according to one of thepreceding claims 18 to 22, wherein the measuring of the datatransmission lines (2-6) is repeated periodically.
 24. The method forinverse multiplexing according to one of the preceding claims 18 to 23,wherein a deactivated data transmission line is selected and activatedto substitute an activated data transmission line, when the connectionparameters of the activated data transmission lines indicate that thedata transmission through this data transmission lines has degraded.